When a patient suffers from an ischemic event in the coronary, peripheral or cerebral vasculature the blood supply to tissues and organs distal to the blockage or occlusion is significantly diminished. The resulting deprivation of oxygen increases the risk of necrosis of the tissues and organs. Generally, a patient suffering an ischemic event is treated by minimally invasive catheterization, such as for example percutaneous transluminal coronary angioplasty (PCTA) if the blockage occurs in the coronary vasculature. PCTA is employed to dilate the ischemic blockage and to restore the blood supply to the tissues and organs. Rapid restoration of blood flow after an ischemic event minimizes the duration of insufficient oxygenation to the tissue and organs, and therefore optimizes tissue and organ survival. However, it has now been found that restoring blood supply in a rapid and consistent manner results in reperfusion injury. A shock to the tissues and organs from rapid oxygen re-saturation and abrupt changes to pH level in the tissue can result in an overall increase in the infarct size.
Reperfusion injury results from the rapid opening of a blood vessel of the coronary, peripheral, and/or cerebral vasculature after a period of ischemia also known as reduced blood flow. For example, the rapid opening of an artery of the heart during a ST-Elevation Myocardial Infarction (“STEMI”), or an artery to the brain (ischemic stroke), or an artery to the other vital organs such as the kidney, liver or other tissues of the body sometimes causes ischemic injury in myocardial, cerebral, peripheral and spinal infarction, for example. One method to reduce or prevent the occurrence of reperfusion injury is a technique known as post-conditioning. Post-conditioning is a method during which the blood flow in the infarcted artery is stopped and started for multiple cycles immediately after re-opening of initial flow from the STEMI or other blockage. This re-opening of blood flow can be either before or after angioplasty, with or without placement of a stent.
Currently, physicians typically use a conventional angioplasty catheter to perform post-conditioning techniques. However, the use of an angioplasty catheter is not optimal for post-conditioning. For example, the angioplasty balloon is not configured to quickly occlude flow, nor is it configured to withstand multiple and sequential inflation and deflation cycles. Instead, the angioplasty balloon is designed to carefully create a new, circular lumen. Additionally, the typical angioplasty balloon is non-compliant, meaning it is designed and/or made of a material that is meant to be inflated with a range of pressures, while not significantly changing its outer diameter size. A typical non-compliant angioplasty balloon becomes circular at approximately 4 atmospheres of pressure. As the balloon pressure is increased, the outer diameter grows very little even as pressure is increased to 14-18 atmospheres. Such balloon characteristics can be drawbacks for post-conditioning. Further, an angioplasty balloon is typically designed to open a stenosis or blood vessel along a lesion, rather than just occlude flow. Thus, the length of an angioplasty balloon is generally between 8 mm to 40 mm, while an occlusion balloon could have a smaller length.
Another major drawback to using a conventional angioplasty catheter for post conditioning is efficiency. Prior to use the physician must measure the blood vessel, for example, by fluoroscopy, then size the balloon both for length and diameter, and then go through various steps to prepare the balloon such as removing the air trapped within the balloon before filling the balloon with saline/contrast mixture. Thus, using the angioplasty catheter with the angioplasty balloon suffers from inefficiencies. Further, the angioplasty catheter typically must be manually actuated to both inflate and deflate the balloon. For example, the use of an angioplasty catheter for post-conditioning usually requires rapid rotation of a screw piston in order to deliver the fluid in a controlled manner, while watching the pressure gage of an Indeflator. Inflation of the balloon to a circular size can require 10-20 twists of the Indeflator in order to expand the balloon. During deflation, the Indeflator is normally directly unlocked and rapidly deflated. If a controlled deflation is required, then the Indeflator can be manually screwed down to a lower pressure. Due to the extent of manual manipulation required to inflate and deflate the balloon, physician-to-physician variability is unavoidable. Thus, over the course of multiple inflations and deflations of the balloon, there will be a great variability in the rise and fall of blood flow in the blood vessel. Normalizing the blood flow, i.e. the rate of inflation, pressure of inflation, and rate of deflation across physicians can be critical to the efficacy of post-conditioning. In addition to the cumbersome nature of actuating inflation and deflation of the angioplasty catheter, the speed of inflation is limited by the physical capability or limitations of the treating physician to rapidly rotate the screw piston. Given that many sequential inflations and deflations are needed during a post-conditioning, use of an angioplasty catheter has many drawbacks. As a result much time is lost in the process of using a conventional angioplasty catheter for post-conditioning.
Use of a conventional angioplasty catheter can also result in significant operator-to-operator variability in inflation time, pressure of balloon, size of balloon, and deflation time. A system which normalizes the inflation time, pressure, size and deflation time is required, while still allowing operator control of the duration of inflation. Lastly, angioplasty balloons, especially rapid exchange balloons, do not have any means to deliver drug distal to the balloon without the added steps of removing the guidewire and later replacing the guidewire.
Additionally, coronary retroperfusion also may be used as to preserve ischemic myocardium. Retrograde blood flow through the coronary venous system may be augmented by coronary ostial occlusion.
A need exists for a catheter system that is capable of reperfusion and retroperfusion to restore blood flow after an ischemic event in an intermittent and gradual fashion with ease and efficiency, while allowing the option of drug delivery distal to the balloon over a standard length guidewire.